The invention relates to an aqueous gel for dressing wounds, as well as to a package for mixing solid and aqueous components and to a method of preparing the gel for application to a wound.
The healing of wounds, such as wounds resulting from injury, surgical wounds or decubitus ulcers, is greatly dependent upon the dressing used. Conventional bandages often do not provide optimum results. In the case of a decubitus ulcer, treatment should include the removal of necrotic tissue and the establishment of an environment that enhances wound healing. Special pressure-relieving or reducing measures should also be taken. A moist dressing is often beneficial. Some of the advantages of a moist wound dressing are the rehydration of dehydrated tissue; increased angiogenesis, i.e., proliferation of new blood vessels; minimized bacterial growth; physical protection; and the maintenance of the proper pH for stimulating the release of oxygen and for allowing proteolytic enzymes to work more efficiently.
In the past, starches in granular form have been applied to wounds and dextrans have been applied as beads or as a paste. Calcium alginates have also been applied to wounds in powdered or granular form. These prior products have certain disadvantages. Powder or granules cannot be applied evenly. Consequently, they do not absorb tissue moisture evenly, causing nonhomogeneous hydration or swelling of the dry granules. Pastes must be spread onto the tissue. Generally speaking, granular absorbent dressings are difficult to remove completely from the wound bed. Dressing changes typically require irrigation of the wound bed to remove the gel granules. The pressure required to spread the paste can be painful or further traumatize the tissue. In addition, an even application is not always easy to achieve because the product retains its plastic character. If made part of a cloth bandage, the dressing may not have intimate contact with the tissue. In the case of a powder, sterility may be difficult to maintain because air containing airborne pathogens will enter the package, replacing and contaminating the powdered product as it is poured from the container.
British patent GB 2 229 443A describes a two component wound dressing that is a mixture of a gel-forming component together with a film forming component. This mixture forms a coherent film over the wound. The composition has to be kept refrigerated prior to use (pg. 3, lines 1-6). The gel former comprises block copolymers of polyoxyethylene-polyoxypropylene sold under the name Pluronic. The film formers comprise hydroxyethylcellulose, hydroxypropylmethylcellulose or polyvinyl alcohol. Unlike the present invention, these compositions have reversible thermosetting gel properties and have to be kept refrigerated prior to use (pg. 11, lines 14-15). The composition experiences a reversible temperature controlled liquid/gel transition at a temperature range of 16xc2x0 C. to 20xc2x0 C. By contrast, the present invention does not revert to a liquid upon heating or cooling and requires no film former, only a gel former. In tests conducted with the composition of the present invention through a range of 13xc2x0 C. to 33xc2x0 C., the gel was found to remain elastic but nonfluid, i.e., in a gelled condition and thus is a solid that is temperature non-reversible. This was shown by applying pressure to the surface of the gel with an instrument. As pressure is increased, the gel will deform and eventually fracture rather than flow around the instrument. Moreover, the hydrocolloid composition of the present invention is stored dry and is mixed with water just before use, preferably under sterile conditions, forming a dispersion which is initially fluid but which sets up without the necessity of a temperature change. The present invention does not contain a film former comprising a cellulose derivative or polyvinyl alcohol.
In view of these and other deficiencies of the prior art, it is a major objective of the invention to provide a sterile wound dressing and package enabling the dressing to be prepared from two components and which is initially fluid to facilitate application to the wound but which, after being applied, will form a stable, elastic gel in situ to protect the wound and maintain a moist environment at the tissue surface. Another object is to provide a dressing that is shelf stable yet is easily prepared and requires no refrigeration. Another object is to provide a gel for dressing wounds that holds its shape through a wide range of temperatures, i.e., that forms a solid that is temperature non-reversible, and can be removed from the wound bed in a solid plug. Still another object is to provide a dressing that will conform to the exact shape of the wound. The term xe2x80x9cwoundxe2x80x9d herein include burn injuries. Yet another object is to provide a package that protects the dressing product, facilitates mixing and allows precise application to the wound. A further object is to provide a moist, initially fluid wound dressing which sets up in situ shortly after being applied, contains a quantity of moisture and, optionally, one or more medications or disinfectants to promote healing.
These and other more detailed and specific objects of the present invention will be apparent in view of the following description setting forth by way of example but a few of the various forms of the invention that will be apparent to those skilled in the art once the principles described herein are understood.